Halogenated butyl interlayer for reinforced elastomeric hose articles

ABSTRACT

A composite reinforced vulcanized elastomeric hose is disclosed including a tube, an outer cover, an interlayer interposed between the tube and cover, and a reinforcement embedded in the hose wall. The outer cover and inner tube are composed of dissimilar polymers not readily bondable to one another, one of which is an EPDM type, and the interlayer is composed of halogenated butyl which securely bonds the dissimilar polymers together and provides a low permeability internal fluid barrier for the hose article with protection to the embedded reinforcement.

This is a division of application Ser. No. 593,591, filed July 7, 1975now U.S. Pat. No. 4,096,888.

BACKGROUND OF THE INVENTION

This invention relates to composite hose articles in which the cover andtube are made of dissimilar polymers normally not readily bondable oneto the other, and to a method of making such hose.

Oftentimes the mode of failure of both high and low pressure hoses, suchas automotive radiator coolant hose, is attack of the embeddedreinforcement by the conveyed fluid after permeation through the innertube layer. EPDM-type terpolymers are being used increasingly as tubestock (and cover stock) in reinforced hose structures particularlybecause of economic considerations as well as resistance which suchterpolymers exhibit against thermal and chemical influences. Despite thefact that EPDM is less permeable to many types of conveyed fluids thanmore frequently used tube stocks, the problem of permeation through thetube (and eventually completely through the hose) and/or attack of theembedded textile reinforcement remains significant.

An additional problem presented by the use of EPDM-type terpolymers hasbeen the lack of building tack and final adhesivity provided by theterpolymers particularly due to the low unsaturation content andrelatively slow cure rates exhibited by the polymers. As a result, thereare very few elastomeric materials which will readily bond directly withEPDM-type terpolymers to form composite articles with adequateinterfacial adherence.

The most relevant prior art known to Applicants at this time includeU.S. Pat. Nos. 3,059,682 to Fischer et al, 3,492,370 to Wirth, 3,651,176to Usamoto et al, 3,660,224 to Cau et al, 3,682,202 to Buhrmann et aland 3,712,360 to Torti et al.

It is a primary object of the subject invention to provide a compositehose article in which either the tube or cover is made of an EPDM-typeterpolymer and is bonded to a dissimilar polymer to which it is notreadily bondable, with the aid of an interlayer which additionally andvery importantly serves as a fluid barrier internally positioned withinthe hose wall, also protecting the embedded textile reinforcement.

SUMMARY OF THE INVENTION

Briefly described, the composite elastomeric hose article of theinvention includes (1) a first heat setting elastomeric annular memberhaving appreciable permeability to the conveyed fluids and composed of acopolymer of mixed mono-olefins and polyolefins (e.g., EPDMterpolymers), (2) a second heat setting elastomeric annular member of amaterial dissimilar from the copolymer and not readily bondabletherewith, one of the annular members serving as an outer cover and theother as an inner tube for the hose composite, (3) a fibrousreinforcement embedded within the hose composite wall and free fromcontact with the first annular member, and (4) an interlayer of a heatsetting halogenated butyl elastomer interposed between and mutuallybonded to each of the inner tube and outer cover, providing a lowpermeability fluid barrier internally within the hose composite.

In another aspect, the invention pertains to a method for making such ahose composite including the steps of: (1) forming a cylindricallyshaped tube of vulcanizable elastomer comprising a copolymer of mixedmono-olefins and polyolefins blended with specified accelerators, (2)applying to one side of a textile layer reinforcement a gum layer ofhalogenated butyl vulcanizable elastomer, (3) positioning the textilelayer about the tube with the gum layer of halogenated butyl interposedbetween the tube and textile layer, (4) applying a cover over thetextile layer composed of an elastomeric material dissimilar from andnot readily bondable to the copolymer, and (5) vulcanizing the thusformed article to produce a composite unitary hose.

The hose articles of the invention encompass various types of reinforcedhoses generally of a flexible nature including, by way of illustration,automotive radiator coolant hose (which will be described with moreparticularity hereafter), heater hose, hydraulic hose, and the like. Theinvention is not limited to any specific type of hose.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more particularly set forth in certain illustratedembodiments by reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary mold with an uncured hose article positionedtherein for producing flexible radiator coolant hose;

FIG. 2 is a fragmentary partial sectional view of a hose made in themold of FIG. 1;

FIG. 3 is an expanded cross sectional view of the wall of the hose ofFIG. 2, viewed along section 3--3; and

FIG. 4 is a longitudinal section of the wall of a conventional hosedepicting an alternative embodiment of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

An illustrative radiator coolant hose made in accordance with theinvention is shown in FIGS. 2 and 3. The hose generally designated at 10comprises a helically corrugated inner tube 12 composed of EPDM-typeterpolymer, having outward helically fashioned valleys 14 and crests 16.At substantially the apex of the crests 16 are disposed convolutions ofspiral reinforcement 18, preferably made of a spirally coiled springpreformed to the desired pitch and diameter.

The outer surface of the hose, which is also helically corrugated, iscomposed of a rubberized fabric cover 20. In accordance with theinvention the cover 20 is in turn composed of a reinforcement 22embedded within an elastomeric matrix including an outermost skim rubberlayer 24 composed of a polymeric material dissimilar from EPDM-typeterpolymers and not readily bondable therewith, together with aninterlayer 26 interposed between the fabric reinforcement 22 and innertube member 12. This tie gum layer 26 is directly bonded to the innertube 12 along their mutual interface 28. In turn, the tie gum layer 26is directly bonded to the outer cover elastomeric layer 24 throughinterstices provided in the fibrous reinforcement.

The tie gum layer 26 is interposed between the inner tube member 12, onthe one hand, and the outer cover 24 and reinforcement 22, respectively,thereby defining a fluid barrier resistant to penetration by any fluidswhich may be conveyed within the hose tube interior 30, and which haspermeated through the tube member 12. In the embodiment of FIGS. 2 and 3the tie gum layer is also directly in adherence to the fibrousreinforcement. In the alternative shown in FIG. 4 the reinforcement 22'is embedded in the cover elastomer 24' and spaced from both the innertube layer 12' and interposed tie gum layer 26'.

A general method of making the above described hose, aside from certaincompounding and curing considerations to be described hereafter, will bedescribed generally in conjunction with FIG. 1 illustrating a preformed,uncured hose assembly located in a mold defined by upper and lowerhalves 32, 33 just prior to vulcanization.

The generally cylindrically shaped tube 12 may be formed in a desiredmanner such as by a continuous extrusion from which desired lengths aresevered. This tube may then be positioned upon mandrel 34 which has alesser outer diameter than the inner diameter of tube 12. Onto the tubeis telescoped a spring and outer rubberized fabric preform. Generallythe spring 18 can be preformed essentially according to well-knownmethods for forming a coiled spring member, and whereby the approximatepitch and diameter dimensions are attained during the spring formingoperation. The rubberized fabric cover 20 may be formed by providing asquare or bias woven fabric 22, for instance, of any desired textilefibrous material and then calendering one side of the fabric 22 with theinterlayer or tie gum 26 as a friction pass, and then calendering theouter cover layer 24 onto the opposed surface of fabric 22, such as by afriction and skim pass, or solely a skim coating. The rubberized fabric20 may then be cut to the desired dimensions and then wrapped upon thepreformed spring coil 18 in such a manner as to maintain the desiredpitch and diameter for conformance to the mold cavities correspondinginternal corrugations.

The preformed fabric and spring assembly may then be positioned over theinner tube 12, the spring convolutions registering with the corrugationsin the mold halves 32, 33, the end caps positioned in place (not shown)and the mold closed. At this point the cure cycle is commenced byintroducing steam internally within the hollow mandrel 34 from inlet 11and then through ports or passageways 36 provided in the mandrel at atemperature and pressure sufficient to blow mold the hose structureagainst the outer mold cavity. Simultaneously the mold cavity platetemperature has been raised by conductance from the press platens (notshown) so that uniform heat and pressure is applied both internally andexternally of the hose structure. In practice, it has been found that170 psi internal steam is satisfactory, and 350° F. external platentemperature is adequate. Heat and pressure cause the elastomeric layers12, 26 and 24 to flow and intimately bond together by vulcanization toform the composite hose article.

In general, the inner tube 12 is composed of a heat setting elastomericcopolymer of mixed mono-olefins and polyolefins and blends thereof,although in the preferred embodiment the tube is composed of EPDM-typeterpolymers. By EPDM-type terpolymers is meant elastomers prepared byinter-polymerizing a monomeric mixture containing ethylene, a highermono-olefin containing 3-10 carbon atoms and a polyolefin which ispreferably a nonconjugated diene. Conventional EPDM elastomers areformed from monomeric mixtures containing ethylene, propylene and eithercyclic or acyclic nonconjugated dienes, for example ethylidenenorbornene and dicyclopentadiene. The molar ratios of ethylene topropylene may vary from about 45:55 to about 75:25.

Compounding to the EPDM-type terpolymer tube or annular member requiresspecial consideration to achieve final bonding between all layers of thelaminate. While the traditional cures, fillers, softeners and ageresistors among other ingredients may be employed in the batch, it hasbeen found that a special combination of accelerators is required toprovide a more uniform cure for the hose composite. In essence, it isnecessary to preferentially greatly speed up the curing process of thetraditionally slow curing EPDM-type terpolymer layer for otherwise theinterlayer of halogenated butyl would cure too fast with respect to theEPDM layer and the interface between such layers would lack sufficientcross-linking for a good bond. It has been found that the followingcombination cure system of ultrarapid accelerators and curing agentsbased on 100 parts of EPDM hydrocarbon provides a cure gradient acrossthe entire hose composite which is of sufficient uniformity to produceexcellent mutual adhesion between the various layers: 2.25-3.75 partstetramethylthiuramdisulfide; 1.25-3.25 parts zinc dibutylthiocarbamate;1-2 parts tetramethylthiurammonosulfide; 1.5-2.5 parts 4,4'dithiomorpholine; and 0.4-0.8 parts sulfur. As is well know, it is alsoadvantageous to incorporate activators with the foregoing, e.g., zincoxide and stearic acid.

The outer cover layer is also composed of a heat setting elastomericmaterial but differs from the EPDM-type terpolymer layer by the factthat it is dissimilar therefrom and does not readily bond to EPDM-typeterpolymers. Whereas the EPDM layer may in the preferred embodiment havean unsaturation content of only about 2-8%, the outer cover layer isgenerally significantly more highly unsaturated, e.g., up to about 25percent unsaturation. Representative examples of suitable outer covermaterials include natural rubber, butadiene-styrene rubbers (SBR),isoprene rubber, nitrile rubber (NBR), neoprene (chloroprene) andchlorosulfonyl polyethylenes. Excluded from this grouping is butylrubber and EPDM itself, as these materials normally form a good bondwith EPDM.

The interlayer according to the invention is preferably a distinctvulcanizable tie gum although the polymer may be applied in other formssuch as a cement. The interlayer will possess a permeability to theconveyed fluid which is substantially less than the permeability to thatfluid exhibited by the EPDM-type terpolymer layer (and also less thanthat of the cover layer). Generally the thickness of the layer need onlybe great enough to provide a fluid barrier interposed between the fabricand EPDM-type terpolymer layer. Thus, in the example of the radiatorhose disclosed in conjunction with FIGS. 2 and 3, a calendered frictionlayer of about 20 mils in thickness on the EPDM side of the fabric hasbeen found sufficient.

According to the invention, the interlayer is composed of a halogenatedbutyl rubber, preferably either brominated or chlorinated butyl. Asignificant advantage of using this type of interlayer is the fact thatits curing time may normally be intermediate that of each of the innertube and outer cover layers to which it is in contact. In this manner, abalanced cure rate may be obtained over the entire composite even thoughthe cure time of the EPDM layer (even with the special combination ofaccelerators) is significantly greater than the cure time for theoutermost cover layer. Thus, by fully curing or slightly over-curing thecover member, and slightly under-curing the EPDM tube layer, there willstill be a strong bond along each of the interfaces between thehalogenated butyl and adjacent layers. A representative formula for theinterlayer is set forth as follows, with parts on a weight basis.

    ______________________________________                                        Component                  Parts                                              ______________________________________                                        Chlorobutyl HT-1066 (contains non-staining)                                    stabilizer, 2% unsaturation and 50-60                                         Mooney viscosity)         100                                                Black N550                 16.20                                              Black N762                 29.60                                              Hard Clay                  46.30                                              Stearic Acid               1.50                                               LM Polyethylene (Allied Chemical -617A,                                        melting point less than 90° C.)                                                                  3.00                                               Sta Tac A-100 (trademark for aliphatic                                         hydrocarbon resin)        8.00                                               Amberol ST 140C (trademark for unmodified                                      phenol formaldehyde resin)                                                                              3.25                                               Process Oil                4.60                                               Zinc Oxide                 5.00                                               Benzothiazyl disulfide     1.40                                               Diphenyl guanidine         .35                                                Sulfur (80% insoluble)     3.36                                               ______________________________________                                    

The reinforcement member which is embedded within the hose article ispreferably a textile layer (woven fabric 22 in the above example) whichhas interstices therein permitting flow through, to some degree, of theadjacent elastomeric layers for intimate bonding contact with oneanother. This reinforcement is normally embedded in the hose wall toprovide the necessary burst resistance and it is thus important toprotect such fabric or other reinforcement from deterioration bypermeating fluids. The halogenated butyl interlayer provides this fluidbarrier function and is generally directly bonded to the fabric, therebyisolating the reinforcement from direct contact with the inner tube. Thefibrous textile reinforcement may be used in various forms, for exampleas a woven fabric, a knit, braid, spiral and the like, formed forinstance of filaments, cords, twisted strands or staple fibers of apolymeric material. The reinforcement may be twined about the inner tubein continuous fashion using a braiding or knitting machine, forinstance, or wrapped on the tube, and in the latter case is preferablyrubberized according to the invention with the interlayer tie gumapplied to one or both surfaces of the reinforcement.

In general, a plurality of layers of reinforcement may be included,however, in the case where multiple plies are employed, the plies shouldnot be in direct contact with one another but should instead beseparated by an insulating layer of elastomeric material, which in thiscase could either be additional halogenated butyl or the materialforming the outer cover, or a material mutually bondable to the coverand halogenated butyl layers.

While it is preferred that the halogenated butyl be in direct contactwith the fabric reinforcement layer, the interlayer may exist as asimple skim layer free from direct contact with the reinforcement (FIG.4) so long as such interlayer is interposed between the EPDM-typeterpolymer layer and the textile reinforcement layer.

In the illustrated embodiment of FIGS. 2 and 3, EPDM was employed as theinner tube layer providing resistance to ozone, thermal influences andin general various chemicals, and neoprene was employed as the outercover particularly for the advantage of releasability from the moldsurface 32 (as contrasted with butyl rubber which was found to stick tothe mold). Such materials may be reversed depending on the desiredapplication. In such reversed case, the halogenated butyl layer would asin the former case be interposed between the tube layer andreinforcement.

It will be understood that the invention is capable of a variety ofmodifications and variations which will become apparent to those skilledin the art upon a reading of this specification, the scope of theinvention being defined by the appended claims.

What is claimed is:
 1. A method for making a textile layer reinforcedcomposite hose article resistant to fluid penetration,comprising:forming a cylindrically shaped tube of vulcanizable elastomercomprising a terpolymer of mixed mono-olefins and polyolefins blendedwith ultrarapid accelerators and curing agent; applying to one side of atextile layer a gum layer of chlorinated butyl vulcanizable elastomer,said gum layer making direct adhering contact with fibers of saidtextile layer; positioning the textile layer about the tube with the gumlayer of the chlorinated butyl elastomer interposed between the tube andtextile layer to produce a preform; applying a cover over the textilepreform composed of an elastomeric material dissimilar from and notreadily bondable to said terpolymer; and vulcanizing the thus formedarticle to produce a composite unitary hose.
 2. The method of claim 1wherein the gum layer of halogenated butyl is applied separately to bothsides of the textile layer so as to directly bond together and embed thetextile layer in the halogenated butyl elastomer.
 3. The method of claim2 wherein the textile layer has interstices therein, permitting flow ofthe halogenated butyl elastomer through such interstices.
 4. The methodof claim 1 wherein the gum layer of halogenated butyl has a cure rate,calculated on an equivalent basis, which is intermediate the cure rateof the tube and cover elastomeric materials.
 5. The method of claim 4wherein the ultrarapid accelerators comprise alkyl substitutedthiuramsulfides, zinc alkyl substituted thiocarbamate, and substitutedthiomorpholine.
 6. The method of claim 1 wherein the gum layer ofhalogenated butyl is applied to the textile layer by calendering the gumlayer on at least one side of the textile layer.
 7. The method of claim6 wherein the calendered textile layer is positioned about the tube bywrapping the calendered fabric about the tube with the calendered layerof halogenated butyl applied adjacent the tube.
 8. A method for making atextile layer reinforced composite hose article resistant to externalgas penetration, comprising:extruding a tube of a heat settingelastomeric material other than butyl rubber or EPDM, and which does notnormally bond to EPDM-type terpolymers; twining a textile layerreinforcement over the tube; applying a gum layer of chlorinated butylelastomer over the textile layer and completely covering the same, saidgum layer being in direct adhering contact with fibers of said textilelayer; extruding or wrapping a cover layer of EPDM-type terpolymer overthe chlorinated butyl layer whereby the interposed halogenated butyllayer acts as a premeability barrier between the textile layerreinforcement and cover of EPDM-type terpolymer; and vulcanizing thethus formed article to produce a composite unitary base.
 9. The methodof claim 8 wherein the textile reinforcement is calendered separatelywith the halogenated butyl elastomer to form a layer thereover, prior topositioning over said tube.